Observation and study of local metastable excitations in rare gas cryocrystals by electron spin resonance

Using the ESR method we have detected and studied unstable paramagnetic excited states formed when products of a gas discharge are captured in a condensing cryocrystal. These paramagnetic centers have been interpreted as metastable 3P2 rare gas atoms which move from the discharge to the growing cryocrystal, become trapped there, and then experience an anisotropic electric field of the crystal environment distorted by this center. It is established that with low gas flow rates to the substrate, the nature and basic characteristics of these centers are the same in the cryocrystals of all the rare gases (Ne, Ar, Kr, and Xe). We used the radio-frequency ESR line saturation method to determine the lower boundary for the lifetime τ of the excited states. These lifetime values are found to be for one type of center in the interval 10−1s >τ > 10−4s, and for another type in the interval 10−1s> τ > 10−2s. Thus, we have apparently detected the most long-lived excited state in rare gas cryocrystals. We found that an additional inert gas flow directed onto the surface so as to bypass the gas discharge affects the efficiency of formation of the unstable centers. Depending on the nature of the rare gas used in the two flows the second flow can either reduce or enhance this efficiency. An assumption is suggested concerning a possible source for the above effect from the auxiliary flow.

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